New Honda mower surging. Is Your Lawn Mower Surging? Here’s the One Simple Fix You Need

Is Your Lawn Mower Surging? Here’s the One Simple Fix You Need

Do you have a surging lawn mower that’s acting up? I’ve been there too and discovered that the most common cause is a blockage in the fuel supply. In this blog post, we’ll dive into other factors causing your “lawn mower engine to surge at full throttle“, as well as providing practical steps on how to remedy these issues.

Stick around for an enlightening journey through the world of lawn mowers!

Key Takeaways

• The most common causes of a surging lawn mower engine include poor gas quality, a clogged fuel cap vent, and a dirty fuel filter.
• Poor gas quality can lead to irregular combustion in the engine, causing it to surge. It is important to use high-quality gasoline to prevent this issue.
• A clogged fuel cap vent disrupts the flow of fuel to the engine and can result in surging. Regularly cleaning the vent is crucial for smooth operation.
• A dirty fuel filter can cause fluctuations in fuel flow, leading to surges. It is recommended to replace the filter regularly for optimal performance.

Causes of Lawn Mower Surging

There are several causes for a lawn mower engine to surge, including poor gas quality, a clogged fuel cap vent, and a dirty fuel filter.

Poor gas quality

Stepping out onto your lawn, you find that your faithful lawn mower is surging. And it’s not due to some mechanical wizardry; instead, it could be as simple as the quality of gas you’re using.

In fact, poor gas quality is a common culprit when a lawn mower engine starts surging at full throttle. Here’s why: low-grade gasoline can lead to irregular combustion in the engine because it degrades faster and may even become contaminated over time — this contamination might be from water condensation or other pollutants.

Now imagine trying to run with one shoe on, awkward right? That’s how your lawn mower feels running on degraded gasoline – its pace fluctuating up and down unevenly like an unsteady jogger.

This irregularity prompts what we call ‘surging’. over, if old or unprotected fuel has idled in your machine for too long, don’t be surprised if this triggers surges too.

So next time think twice before filling up with any ol’ gas – Your choice of fuel can essentially make or break the smooth operation of your beloved landscape companion! To keep those unwanted engine hiccups at bay and ensure a seamless mowing experience each time – opt for premium-quality gasoline whenever possible.

Clogged fuel cap vent

Imagine this: Your lawn mower engine is surging, revving up and down as if it has a mind of its own. You’re not alone; many unsuspecting homeowners face this issue. Allow me to explain one potential cause – a clogged fuel cap vent.

Most lawn mowers have tiny vents on their fuel filler caps. These vents play an essential role in maintaining the correct vacuum and pressure inside the fuel tank, ensuring your lawn mower runs smoothly without any annoying stuttering or surging.

But sometimes, dirt or debris can block these little vents, disrupting the steady flow of fuel to your engine. The result? Your once reliable lawn mower engine surges at full throttle.

The situation gets worse when there’s improper back pressure in the fuel tank due to a clogged vent causing the gasoline pressure to oscillate between extremes resulting in noticeable fluctuations – effectively making your lawn mower engine surge up and down.

That said, keeping your fuel cap vent clean is crucial for a smooth-running machine! Just like regular oil changes and spark plug replacements, cleaning out this tiny but mighty component should be part of your routine maintenance checklist.

After all, who wants their serene Sunday morning disrupted by a surging lawn mower?

So next time you notice that familiar lull-and-roar pattern indicating your lawn mower is surging again, do check if it’s just another case of dirty fuel cap vent before diving into other possible causes.

Dirty fuel filter

Owning a lawn mower, you’re likely familiar with the engine surging and how disruptive it can be. One common culprit is a dirty fuel filter. This unassuming component plays a critical role in maintaining your lawn mower’s performance by ensuring only clean fuel reaches the carburetor.

Over time though, dirt and debris can clog this filter, disrupting the steady flow of gas from the tank to your lawn mower engine which causes it to surge up and down at full throttle.

That hiccuping or stuttering sensation you feel? It’s often tied directly back to this issue! To fix this, simply replace your old fuel filter with a new one; an easy task that enhances proper functioning of your machine while minimizing instances where your lawn mower is surging due to blockage in its fuel system.

Solutions to Fix Lawn Mower Surging

To fix a surging lawn mower, start by removing any bad gasoline from the fuel tank. Then, clean the fuel cap vent to ensure proper airflow. Finally, swap out a dirty or clogged fuel filter with a new one.

Removing bad gasoline

If you notice your lawn mower surging, one possible culprit could be bad gasoline. Using old or contaminated gas can cause engine surges, often due to water condensation. To address this issue and get your lawn mower running smoothly again, follow these steps:

• Drain the existing gasoline: Begin by safely draining the old gas from your lawn mower’s fuel tank.
• Locate the fuel line: Find the fuel line that connects the tank to the carburetor.
• Disconnect the fuel line: Carefully disconnect the fuel line from either end, taking note of its position for reattachment later.
• Prepare a container: Place a clean container or gas can under the disconnected fuel line to catch any remaining gasoline.
• Drain the remaining gas: Tilt your lawn mower so that the remaining gasoline flows out of the fuel tank and into the container.
• Dispose of old gas properly: Once all the old gas has been drained, dispose of it properly according to local regulations or guidelines.
• Clean out the fuel system: With fresh fuel now needed, make sure to thoroughly clean out any debris or residue in your lawn mower’s fuel system.
• Refill with fresh gasoline: Fill up your lawn mower’s tank with fresh, high-quality gasoline.
• Reattach and secure the fuel line: Reconnect the previously disconnected fuel line securely to both ends – ensuring a tight fit and no leaks.

Cleaning the fuel cap vent

Cleaning the fuel cap vent should be done regularly to prevent surging in your lawn mower engine. Here’s how to do it:

• Remove the fuel tank cap from your lawn mower.
• Inspect the cap for any debris or dirt that may be blocking the vent.
• Use a small brush or cloth to gently clean the vent, ensuring that it is free from any obstructions.
• If the vent is still clogged, you can use compressed air to blow out any remaining debris.
• Once the vent is clean, carefully reattach the fuel tank cap to your lawn mower.

Swapping out a fuel filter

One of the solutions to fix a surging lawn mower engine is by swapping out the fuel filter. A clogged fuel filter can cause issues with the flow of fuel to the carburetor, leading to fluctuating revving and surging of the engine. If you notice your lawn mower surging at full throttle or the engine surging up and down, it may be time to replace the fuel filter.

• Improved Fuel Flow: A clogged fuel filter restricts the flow of fuel to the carburetor, affecting its performance. By replacing it with a clean one, you ensure a steady flow of fuel without any interruptions.
• Enhanced Engine Performance: When the carburetor receives a consistent supply of clean fuel, it can mix it properly with air and provide smooth combustion. This leads to better engine performance and reduced surging.
• Prevention of Damage: A clogged fuel filter can lead to harmful particles or debris reaching sensitive components such as valves or injectors. By swapping out the filter regularly, you protect these vital parts from potential damage.
• Reliable Operation: A new fuel filter ensures that only clean fuel enters the carburetor and other engine parts. This helps prevent sudden stalling or erratic behavior during operation.

Conclusion

In conclusion, if you find that your lawn mower is surging, there are several potential causes to consider. Poor gas quality, a clogged fuel cap vent, and a dirty fuel filter are common culprits.

Fortunately, these issues can be resolved by removing bad gasoline, cleaning the fuel cap vent, and swapping out a fuel filter. By addressing these underlying problems, you can ensure that your lawn mower operates smoothly and efficiently.

FAQs

What causes a lawn mower to surge?

A lawn mower can surge due to a variety of reasons, including clogged fuel lines or filters, a dirty carburetor, an improperly adjusted throttle, or issues with the spark plug.

How can I fix a surging lawn mower?

To fix a surging lawn mower, you can start by cleaning or replacing the air filter and spark plug. Check for any debris in the fuel line and clean or replace it if necessary. If the issue persists, you may need to clean the carburetor or adjust the throttle settings.

Can bad gasoline cause my lawn mower to surge?

Yes, bad gasoline can contribute to your lawn mower surging. Old or contaminated gasoline can lead to clogs in the fuel system which disrupts proper engine performance.

Should I seek professional help if my lawn mower continues to surge after troubleshooting?

If your best efforts at troubleshooting have not resolved the surging issue with your lawn mower, it is recommended to seek professional help from a qualified technician who specializes in small engines. They will be able to diagnose and repair any underlying problems accurately and efficiently.

Lawn Mower Engine Surging – Check this easy fix first!

Lawnmower engine surging is a right pain in the Jacksie; it’s an engine that runs erratically and revs up and down by itself uncontrollably. In some cases, it may only happen under certain conditions, for example, only after the mower gets hot or only when the fuel level gets low.

So what causes the lawnmower engines to surge? The most common reason for a surging lawn mower engine is a blockage in the fuel supply, but there are other possibilities:

Often you’ll find playing around with the throttle helps or applying some choke. You are not on your own; this is a regular complaint. In this guide, we will cover the diagnosis, likely causes, and solutions.

Try the easy fix first – replacing/cleaning gapping the spark plug before attempting carburetor work. If your mower engine is a Honda or Kohler, the fix is simple. Honda and Kohler’s surging is commonly caused by a blocked idle jet see “Gas starvation” towards the end of the page.

If you need more help, check out the “How to fix a surging mower video.”

If your surging mower is a Honda, check out the “Honda mower surging video.”

For many mowers, the fix is to replace the carburetor, and as carburetors are inexpensive, it just makes sense to swap it out and save a ton of messing around. You can check out the quality carburetors available and conveniently delivered to your door by Amazon.com.

Need more info on the fuel system, carburetor components, and how they work, you can check them out here.

Briggs Stratton Surging

Surging BS Classic 450, 500, or 550Some engine types are famous for surging; the Briggs Stratton 450, 500, and 550 series engines are fitted with a metal fuel tank and priming bulb-style carburetor. If you have one of these types of engines and it’s surging – You’re in the right place.

If you don’t have this type of carburetor, skip this section and jump to “Surging Test” below. These engines are fitted with a metal fuel tank and carburetor combination. The gasket sandwiched between the tank, and carburetor distorts over time, allowing a vacuum leak.

The vacuum leak causes the surging; replacing the gaskets and cleaning the carburetor/tank will leave it like new, I promise. In this tutorial, we’ll remove the tank/carburetor unit, clean it and replace the gaskets. Just some basic tools are needed, but get yourself a can of carburetor cleaner; it makes the job a lot easier.

In the workshop, I use WD40 carb cleaner, and you can check out all the tools and parts I use here on the “Small engine repair tools” page.

Tools You’ll Need

Here’s a short list of tools you’ll find useful to complete the task of fixing your surging mower. These tools aren’t essential, but they do make the whole job a ton easier; you’ll need:

Fuel treatment – Every small engine owner should use gas treatment. Most people don’t know gas goes off, and gas left in small engines can cause real problems, as you already know.

Using a gas stabilizer will keep the gas in your mower and your gas can fresh for up to two years.

Carburetor gasket – If you’re fixing the BS Classic engine, then you’ll need this gasket set.

Complete carburetor – As an alternative to replacing your BS Classic carburetor gasket, replace the complete carburetor instead; it includes the replacement gasket.

Manifold – This will only be needed if you have confirmed it has failed. Note there are a few different types of manifold pipe, so be sure to check before ordering.

You can check out all these tools on this page “Carburetor Surging Repair Tools.”

This carburetor style is fitted to a few engines and is prone to gasket failure. The job of replacing is simple and will solve the surge. The process is as follows:

Remove the spark plug wire – prevents the mower from starting.

Remove – Remove and clean the air filter and filter housing – Clean it using soapy water, and when dry, smear some engine oil over the surface of the foam. This helps trap dirt.

Remove tank bolts – They hold the fuel tank to the engine.

With fuel tank bolts removed – pull the tank unit straight out gently and remove the governor control link.

Remove the black rubber elbow crankcase breather pipe. Remove the manifold seal and keeper ring. Sometimes they will come loose and get stuck on the manifold pipe.

Remove – Remove carb screws from the carburetor and set aside.

Using a can of carburetor cleaner – clean all the ports on the surface of the fuel tank.

Empty the tank and rinse it out with fresh gas.

Pull the Siphon from the carburetor; they can be stubborn. Remove both gaskets and use carburetor cleaner to clean the siphon metal filter and all ports of the carburetor. Check the primer bulb for damage; mice like to eat them.

Spray – Spray the carburetor with carb cleaner.

Remove – Remove old gaskets and discard them.

Careful of this spring; it lives under the gaskets, and it can drop off and be tricky to find, as I know only too well.

The gasket is a two-part kit; the rubber-type gasket faces the tank. (carb fitted here for demo only)

The Siphon pushes back into the carb with a click. If you don’t hear the click, it’s not right – try again.

Refit the carburetor to the tank. Don’t over-tighten the screws, as this will distort the gasket. Fit manifold seal and keeper. Smear a small amount of oil on the seal; it helps it seat.

Clean the intake manifold. The grey tube in this shot is manifold. Inspect it for any signs of damage; they are prone to cracking. This will also cause a surge.

To fully inspect the pipe, you need to remove the pull assembly.

I would only do this if there was obvious damage to the manifold or if I had replaced the carburetor gasket and the engine was still surging.

This manifold is cracked and will cause a surge.

Before refitting the tank, fit the keeper ring and O-ring seal. Lube the seal before refitting the gas tank.

Offer the carb/tank unit up to the manifold and attach the governor link and spring. Now push the unit firmly onto the manifold. Fit both bolts.

Refit the air filter and spark plug wire. Use only fresh gas; make sure your gas can is clean. Gas older than three months is stale.

If, after fitting the gaskets, you still have a surge – Replace the Manifold.

Surging Test

As you know, gas starvation causes an inconsistent flow of fuel which in turn causes erratic running. And you also know a vacuum leak will cause erratic running, but it is a much less common cause; however, some carburetors are prone to vacuum leaks.

As engine manufacturers strive to make their engines more efficient, they have also made the carburetors more likely to clog; this has become a common issue.

To quickly diagnose which problem you have, a clogged carb or vacuum leak, follow this simple test.

You will need a helper to hold the bail lever or improvise with duct tape. CAUTION careful where you place your fingers and toes; the engine will be running, so the blade will be spinning.

Your mower will have a Manual choke, Auto choke, or a Primer bulb. Identify which type your mower has; the test is slightly different for each.

If you have a manual choke – apply half choke with the engine running.

If the engine now runs without surging – Gas starvation is the likely fault. If it runs just the same – A vacuum leak is a more likely fault.

If you have an Auto choke – Remove the air filter cover and filter – place a clean rag over the intake while the engine is running.

If the engine now runs without surging – Gas starvation is the likely fault.

If the engine runs just the same – A vacuum leak is the more likely fault.

If you have a primer bulb – you can still do the test – while the engine’s running (need a helper); give it some extra gas by pressing the bulb.

If the engine now runs without surging – Gas starvation is the likely fault.

If it runs just the same – A vacuum leak is a more likely fault.

Gas Starvation

If the test revealed gas starvation, it also showed that your problem is likely a dirty fuel jet in the carburetor, or the gas may be stale or contaminated by water.

Cleaning the main jet usually does the job.

Idle Jet Surging – Honda and Kohler use a relatively easy-to-access idle jet that clogs up and causes surging. The Kohler is easier to access than the Honda.

The Kohler is easier to access than the Honda.

Briggs has fitted a plastic carburetor to a range of engines which also clog up and cause surging.

All of these carburetors can be repaired by cleaning, which I’ve covered previously in videos (links below). Videos cover step-by-step removal, cleaning, refitting, and adjusting your carb.

Fixing this is not difficult. Sometimes you can get lucky by just draining and cleaning the gas bowl, which only takes a few minutes.

I have written a complete guide to Carburetor cleaning with pictures; it includes the gas bowl clean-out, which, as said, is worth trying first.

If cleaning doesn’t work out for you, go ahead and swap out the carburetor for a new one. Check out “New lawn mower carburetors page,” here, I’ve listed good quality replacement carburetors for all the most popular engines.

Carburetors aren’t expensive; messing around with them doesn’t make sense.

You might find this page helpful too – “Carburetor repair tools” I’ve listed some really useful tools that make the job easy. Some of these tools I’ll bet you already have some.

But do try cleaning the gas bowl before removing the carburetor.

Finding a Vacuum Leak

Air that enters the combustion chamber without passing through the carburetor is un-metered. This means the fuel-to-air ratio is unbalanced and, in turn, causes erratic engine performance.

When air sneaks in like this, it causes the engine to run lean (lacks gas). A lean engine runs hot, which isn’t good for an engine, especially an air-cooled one.

Vacuum leaks usually occur because of damaged gaskets. Gaskets are sealing materials fitted between the mating surfaces of engine components. Their function is to create an airtight seal.

They are commonly made from paper, felt, cork, Teflon, neoprene, metal, and rubber. The material type is dependent upon where the gasket is to be used.

Gaskets wear out and break down, and that causes surging.

Extreme Caution – You need to be careful, the engine will need to be running, and so the blade will be spinning when running this test.

A vacuum leak check is performed with the engine running and a can of carburetor cleaner; WD40 works, too, (is there anything WD can’t do?)

Spray the cleaner around all carburetor gaskets anywhere the carburetor meets the engine. The trick is to hear an instant change in engine note; that’s the sign of a vacuum leak.

This can be challenging; you must train your ear to notice the instant change in engine note (and not the surging).

Just do a small section at a time; this will allow you to pinpoint the failure area. Jumping the gun and replacing gaskets without finding the actual leak may work out for you or leave you with the same problem after the rebuild.

You’re right in thinking carburetor gaskets usually cause the problem, but other components, such as manifold pipes, can crack or become loose, causing surging.

Fixing A Vacuum Leak

If a leak is detected, replace all carburetor gaskets, and as you have the carburetor removed, go ahead and clean it. Replacement gaskets are available online; you will require the make and model numbers from the engine.

All manufacturers will have a model number printed on a sticker placed on the body or on the engine. Have a poke around; you’ll find it. Most engine manufacturers will stamp the model numbers in an accessible area. Briggs Stratton stamp their numbers on the metal engine cover.

A new carburetor comes with new inlet gaskets; I like to fit original parts where I can; they fit and are guaranteed.

If, after replacing the carburetor gaskets, the engine still surges, you’ll need to go a little further and replace the manifold intake and gasket.

It’s not a big job, and they don’t give a lot of trouble, but they do crack as they get older. I wrote a step-by-step guide showing you everything you need to know – “Briggs Manifold Replacing.”

Related Question

Honda lawn mower surging fix? To fix a surging Honda lawn mower engine, clean the carburetor, gas tank, and fuel filter. Use fresh regular gas or e10. What causes a lawnmower to run slowly? The most likely cause is a throttle linkage bent out of shape by bumping into the shrubbery or a throttle spring has detached itself.

Hey, I’m John, and I’m a Red Seal Qualified Service Technician with over twenty-five years experience.

I’ve worked on all types of mechanical equipment, from cars to grass machinery, and this site is where I share fluff-free hacks, tips, and insider know-how.

And the best part. it’s free!

What causes lawn mower engine surging?

Fuel system problems or vacuum leaks through the air intake manifold are typical causes of lawn mower surges.

Here’s a rundown of the specific issues causing small engines to quickly cycle between idle speed and full throttle:

• Contaminated gasoline. Old gas or gasoline contaminated with water can cause engine surging.
• Clogged fuel tank cap vent. The fuel tank cap vent can get clogged with dirt or debris. The fuel cap vent helps keep gas flowing smoothly to the carburetor. When it’s clogged, the engine can surge.
• Dirty air filter. The carburetor won’t get a good supply of air when the air filter gets clogged with dust and dirt.
• Worn or damaged air intake gasket. The mower surges when the carburetor sucks air through an unsealed gap in the air intake manifold instead of through the air filter.
• Dirty carburetor. Clogged fuel jets inside the carburetor commonly cause the lawn mower engine to surge. Clogged jets can’t provide the right mix of air and fuel to the engine.

Troubleshooting a lawn mower that is surging

To find the cause of a surging engine, first check the basic issues described above.

• If fuel in your mower’s gas tank is older than six months or you left the lawn mower out in the rain, move the mower to a well-ventilated area and drain the tank. If you see water in the drained gas, you’ll also need to remove the bowl from the bottom of the carburetor and dispose of that gas.
• Check the air vent on the fuel tank cap. Clear the vent hole if it’s clogged.
• Replace or clean the air filter if it’s dirty.

If these basic troubleshooting tips don’t help, then you’ll likely need to make one of the repairs described below.

How do you fix a pulsating lawn mower?

Move the lawn mower to a well-ventilated area and take these steps to fix the engine.

• Remove the air filter and its housing. Check the air filter housing gasket and replace that gasket if it’s worn or damaged.
• If that gasket is okay, check the gasket and seals between the carburetor and the engine. Replace any worn or damaged seals or gaskets.
• If external carburetor seals and gaskets are okay, then you’ll need to rebuild or replace the carburetor. Replacing the carburetor is a much easier repair that rebuilding the carburetor. Follow the steps in our How to replace a lawn mower carburetor repair guide/video to install a new carburetor. If the replacement carburetor for your engine is unavailable, or if you prefer to rebuild the carburetor, order the rebuild kit for your carburetor and follow the steps in our How to rebuild a lawn mower carburetor repair guide/video to clean and rebuild the engine’s carburetor.

How much does fixing a surging lawn mower engine cost?

If you can troubleshoot the surging engine and don’t have to buy parts, the cost of fixing your lawn mower typically isn’t more than the price of replacing the gas.

If you have to buy parts such as an air filter, carburetor or carburetor rebuild kit and you complete the repair yourself, the cost of fixing a surging lawn mower won’t be much more than the cost of the repair parts. The most expensive part that you would have to buy would be the carburetor. You’ll pay about 50 for the replacement carburetor on many common lawn mower engines.

When you have to take the lawn mower to a repair shop to get it fixed, then the repair will typically cost between 50 and 100 to fix a surging engine.